FALLUJAH, Iraq, April 9 -- Two years ago, Cpl. Justin Soule rushed across the Tigris River bridge into Baghdad with the Marines who first entered the city and toppled a statue of President Saddam Hussein. During a bloody uprising that swept Iraq last April, he and his battalion fought their way into insurgent-held Fallujah before commanders ordered a halt.

Today, the infantry squad leader from Itasca, Tex., is back for a third tour in Iraq, living in a bombed-out soda factory, surviving on packaged meals and junk food and admitting that he thinks more about his own liberation than Iraq's.

"I don't really care for the desert, the flies, the dust storms, the trash on the side of the road with kids playing in it," he said as he sat on his bunk this week in the dank, 25-foot-wide room he shares with 13 other Marines. "I'm ready to get out. I'll have a taste of the freedom I've been fighting for."

Soule proudly counts himself among the "Darkside" -- the battle-weary 3rd Battalion, 4th Marines -- the first U.S. military unit to serve three rotations in Iraq. About two-thirds of the battalion's 800 men are on their third tour, having spent more time in Iraq over the past two years than at home.

Like many of his comrades, Soule is a 9/11 Marine, driven to join the corps by duty or outrage after the terrorist attacks in the United States in 2001.

Yet over the course of two years, fighting in Iraq has robbed these young Marines of buddies, left their bodies scarred and tired, and snatched away their innocence. Last week, the conflict stole another Marine from the 3rd Battalion, the 11th killed so far as fatalities among U.S. troops grew to 1,543.

Many Darkside Marines, feeling the pull of family and civilian life, say they don't plan to reenlist for what will inevitably mean more combat zone deployments. A far smaller number say they live for being at war and vow never to leave.

On the anniversary of Baghdad's fall, Marines described the war with stories of euphoria and helplessness, of bitterness and hope and the toll on the lives of U.S. troops.

Lt. Brian Sitko watched the glow of munitions exploding on the horizon, creating the surreal appearance of a sunrise as U.S. forces launched their invasion of Iraq in 2003. He pulled out a pen and paper and wrote a letter to his wife, then slipped it into his chest pocket.

As the Marines battled north, the possibility of death accompanied Sitko as "a daily presence, a fear you have to manage," he recalled in an interview. At war for the first time, many Marines in their teens and twenties grew up overnight, he said. "Childhood is lost, and innocence is left behind."

Officers warned the Marines to expect heavy casualties as they thrust into Baghdad. But they were surprised to find their push into the city relatively unopposed. Instead, some Iraqis offered flowers, candy and a sense of purpose to Marines who say now they were uncertain what they were fighting for.

At Baghdad's Firdaus Square, Marines from the battalion used a chain and a tank-recovery vehicle to pull down Hussein's statue, unleashing jubilation among the crowd. A portly, balding Iraqi man, sweat streaming down his face, approached Sitko to give him flowers and a hug. Sitko said he suddenly remembered an Iraq guidebook that said kissing another man on the forehead signified high respect. In an instant, he pulled the man toward him.

"I gave him a smack on the forehead," he said. "It was probably one of the more gross moments for me, but it was something I wanted to do. He lit up even more. It was so joyous."

Within hours, though, the mood gave way to chaos as looters swarmed the city.

Soule recalled looters invading a hospital that his unit was trying to guard. "We ran them off, but they kept coming back," he said. "They'd cut their arm on one side breaking into the hospital looting and then come in another door to get medical care."

The confusion made the Marines feel helpless and unprepared. "We weren't a police force. We didn't know how to deal with it," Sitko recalled.

Driving through the city in a Humvee with three other officers, he spotted a man with an AK-47 rifle in an electronics store. In an effort to protect the surrounding crowd, Sitko and the others got out of the Humvee and disarmed the man.

"They all applauded," he said. "We had cleared the way for them to loot."

When the battalion received a second call to Iraq in late 2003, many of the troops felt ambivalent. "We'd already been to a war, we were just going to a combat zone," said Lance Cpl. Michael Hinson, 21, an M-249 machine gunner from Odessa, Tex.

Yet with the insurgency in full swing, the unit faced some of its toughest battles yet. In early April 2004, it was abruptly ordered to Fallujah to take part in an assault on the city a few days after four American contractors were killed and mutilated there.

The unit pushed three blocks into Fallujah but was halted when U.S. and Iraqi officials ordered the assault aborted. The Marines say they and their commanders felt intensely disappointed.

"I believe we should have pushed through Fallujah then. We would have been a lot more successful, and there would have been a lot less bombing," Hinson said at a camp on the outskirts of Fallujah, where thousands of homes were destroyed in a large-scale offensive in November.

Soon after the Darkside arrived in Fallujah last year, one of Hinson's close friends, Lance Cpl. Torrey L. Gray, was killed by sniper fire. "The moment I will never forget is when our sergeant came up and said [Gray] was fatally wounded," said Hinson. "We were like brothers."

A month later, Hinson almost died as well. A bomb exploded under his convoy, hurling shrapnel into the vehicles. Hinson lost sight in his left eye. "We just heard a beep, not a boom or anything. Then it was a blur," he said. "We had nine Purple Hearts."

In January, the battalion was called to Iraq again, ordered to deploy about a month earlier than anticipated to help provide security for Iraq's elections. The news was unwelcome but not entirely unexpected -- some of the Marines say they had kept their duffle bags packed.

U.S. policymakers "didn't have the foresight of seeing that it wouldn't be an easy war. They didn't think it out," said Soule, listening to Texas country music as he took a break one recent evening in his cramped room at the gutted Fallujah soda factory.

Conditions at the camp in downtown Fallujah are austere compared with many bases in Iraq today. With the staple food still packaged meals-ready-to-eat (MREs), Soule and his buddies say they prefer to survive on cheese puffs, PayDay bars, CornNuts and other junk food sent from home.

Infrequent showers are taken by filling a black plastic bag with water, letting it warm in the sun and suspending it for a brisk splash. Lacking even a portable toilet, the Marines dispose of human waste in "wag bags" and later burn them.

Soule and others said such conditions were actually a step up from past tours. "This is the best setup we've had. This is pretty good," he said.

Pinups, race-car photos and beer ads liven up the walls of an otherwise drab room, its windows blocked by sandbags. In brief breaks between 10- to 12-hour shifts patrolling Fallujah or pulling guard duty, the Marines watch movies, play Monopoly and smoke cigarettes. The close quarters sometimes lead to arguments and shoving matches. Some Marines let off steam by hacking away at palm trees on the base with an ax.

"Problems stem from people just being tired of being over here," Soule said.

The Marines said few among them planned to reenlist. Those who did, such as Hinson, were signing up for so-called non-deployable jobs such as teaching or administration. "I don't think there's a lot of Marines who want to come back to Iraq every six months," said Cpl. Scott Rolston, who plans to return to his native Anchorage to join the highway patrol or fire department.

Family pressures are mounting on many Marines -- especially those who, like Hinson, are married and have babies on the way.

Lance Cpl. Dan Despain, 26, of St. Louis, gazes at a handful of laminated photos of his infant daughter before he beds down each night. "I've missed seeing her crawl, hearing her start talking and saying 'Da Da.' I'm not going to be the type of parent who isn't there when she needs me," he said.

Still, none of the Marines said they regretted their service in Iraq, despite what they consider missteps in a war that they anticipate could drag on for five, 10 or even 20 years.

"A lot of people made the ultimate sacrifice, but they did it saving other people," said Cpl. Shawn Rodgers, of Owensville, Mo., who plans to leave the corps for college. "It's an all-volunteer force. And whether they realize it or not, this is what you join the military to do. You either love it or you hate it."